Characterization of the wear particles of human diarthrodial joints will be further pursuud, using the technique of Ferrography. In particular, we shall seek to ascribe particular wear modes to the production of those types of particle whose derivation is presently unknown. Once the origins of the various different particles are understood, the goal of correlating the results of Ferrographic analysis of synovial fluids with specific joint diseases, thus giving it diagnostic value, will become more realistic. Investigation of the cellular response to wear particles is proving fruitful. These present studies will be extended to give a fuller account of the enzymes released or activated in response to wear particles, and their physiological significance. The enzymes collagenase, neutral protease(s), and lysozyme will be given particular attention in this respect. Synovial cells and macrophages are the cell types being used for these in vitro studies.